Top Four Signs of Feline Hyperthyroidism to Look For Feline hyperthyroidism, caused by excessive production of thyroid hormones, is a common condition in older cats. But unlike well-known conditions and diseases such as Rabies, it can be difficult to spot feline hyperthyroidism as symptoms can start slowly and be subtle. Some are often falsely attributed to aging by well-meaning owners. Cat hyperthyroidism can be deadly if left untreated. But it doesn’t have to be. If it is caught early, most cats can fully recover through feline hyperthyroidism radioiodine treatment. As a pet owner, it’s important to keep an eye out for the most common feline hyperthyroidism symptoms. If you’ve noticed these changes in your cat, make an appointment with your veterinarian right away. Excessive thirst and increased urination This is a common feline hyperthyroidism symptom, occurring in approximately one half of all cats diagnosed with feline hyperthyroidism. It can also indicate kidney problems. Either way, cats exhibiting this feline hyperthyroidism symptom should be taken to the veterinarian. Increased appetite and weight loss If your cat is eating more but losing weight, he may be exhibiting a symptom of feline hyperthyroidism. Because the thyroid helps regulate metabolism, sudden changes in food intake and weight can be cause for alarm. However, this typically occurs early in the progression of feline hyperthyroidism. If you can catch a feline hyperthyroidism symptom quickly, you increase the chances of successfully treating your cat. Anxiety Signs of anxiety in a cat – including pacing, yowling for no apparent reason, and restlessness – are a common symptom of feline hyperthyroidism. This is due to increased stimulation in the nervous system which is a common occurrence in cats with feline hyperthyroidism. Changes in coat Cats with hyperthyroidism often experience changes their coat. For cats with long hair, their coat will often appear dull, matted, and unkempt. Cats may also groom obsessively, leading to bald spots. This list of feline hyperthyroidism symptoms is not exhaustive, but it should provide a good starting point for concerned pet owners. Remember, feline hyperthyroidism is often treatable when caught early. If your cat is exhibiting these symptoms, it’s time to schedule an appointment with your veterinarian. More on feline hyperthyroidism symptoms. **Back to Feline Hyperthyroidism: An Overview back to top
Rapid heart rates are common in cats with hyperthyroidism, and heart murmurs and high blood pressure can also occur. Cats with hyperthyroidism that are not treated often develop a heart condition called hypertrophic cardiomyopathy, in which the muscle of the heart becomes excessively thick. This can lead to heart failure and death. How is feline hyperthyroidism diagnosed? There are three main criteria for diagnosing hyperthyroidism: Clinical signs as described above Palpation of an enlarged thyroid gland – Normally, the thyroid gland in cats cannot be palpated. In most cats with hyperthyroidism, the gland becomes large enough to feel. Sometimes the gland becomes so large, it actually migrates or “sinks” into the chest cavity, and cannot be felt. There may also be instances where thyroid gland tissue is found in other areas of the neck and chest. This is called ectopic thyroid tissue. Increased thyroid hormone levels – High T4 levels indicates hyperthyroidism in cats. Elevated T3 levels also indicate hyperthyroidism, however, in 25% of the hyperthyroid cats T3 is not elevated even though T4 is high. For this reason, the blood level of T4 is primarily used to diagnose hyperthyroidism. Sometimes, an animal with concurrent kidney, heart, or other debilitating disease may have hyperthyroidism but a normal or only slightly elevated T4. If an animal is suspected of having hyperthyroidism but has a normal blood test it is suggested that the animal be re-tested after the current disease is under proper medical management. Since many of the signs of hyperthyroidism can also be found in other diseases such as diabetes mellitus, kidney failure, heart disease, or liver disease, other laboratory tests such as a CBC, serum chemistry, and urinalysis are generally performed to determine if these diseases are present. The test results will also influence which type of treatment would be most appropriate. Cats with hyperthyroidism may have slight increases in the number of red blood cells, increased liver enzymes, and increased BUN and creatinine, which measure kidney function. Occasionally, veterinarians will use other tests to confirm their diagnosis of hyperthyroidism. These include the T3 suppression test, thyrotropin-releasing hormone stimulation test, measurement of free T4, and thyroid radionuclide uptake and imaging. How is feline hyperthyroidism treated?
The following information isn’t intended to replace regular visits to your veterinarian. If you think your cat may have hyperthyroidism, please see your veterinarian immediately. And remember, please do not give any medication to your pet without talking to your veterinarian first. What Is Hyperthyroidism? Hyperthyroidism is the most common glandular disorder in cats. It is most frequently caused by an excessive concentration of circulating thyroxine-a thyroid hormone better known as T4-in the bloodstream. What Are the Symptoms of Hyperthyroidism? Weight loss and increased appetite are among the most common clinical signs of this condition. Weight loss is seen in 95 to 98 percent of hyperthyroid cats, and a hearty appetite in 67 to 81 percent. Excessive thirst, increased urination, hyperactivity, unkempt appearance, panting, diarrhea and increased shedding have also been reported. Vomiting is seen in about 50 percent of affected cats. Clinical signs are a result of the effect of increased T4 levels on various organ systems. What Breeds/Ages Are Prone to Hyperthyroidism? Hyperthyroidism can occur in any breed of cat, male or female, but occurs almost exclusively in older animals. Less than 6 percent of cases are younger than 10 years of age; the average age at onset is between 12 and 13 years. How Is Hyperthyroidism Diagnosed? Because several common diseases of older cats-diabetes, inflammatory bowel disease, intestinal cancer and chronic kidney failure-share some of the clinical signs of hyperthyroidism, a battery of tests is in order. A CBC, chemistry panel and urinalysis alone will not diagnose hyperthyroidism, but they can certainly rule out diabetes and kidney failure. Hyperthyroid cats may have normal findings on the CBC and urinalysis, but the chemistry panel often shows elevation of several liver enzymes. In the vast majority of cases, a definitive diagnosis of hyperthyroidism is based on a simple blood test that shows elevated T4 levels in the bloodstream. Unfortunately, between 2 percent and 10 percent of cats with hyperthyroidism will have normal T4 levels. One possible explanation for this is that in mild cases, T4 levels can fluctuate in and out of the normal range. Another is that concurrent illness will suppress elevated T4 levels, lowering them into the normal or high-normal range and fooling the veterinarian into thinking that the cat’s thyroid status is normal. Because these are geriatric cats, concurrent illness is fairly common, and diagnosis of hyperthyroidism in these cats can be tricky.
Hyperthyroidism – Excess Thyroid Hormone in Cats Hyperthyroidism in Cats Hyperthyroidism is a disease caused by overproduction of thyroxine, a thyroid hormone that increases metabolism in the body. The thyroid gland normally produces thyroid hormones in response to stimulation by the pituitary gland, the “master gland” of the body. Thyroid hormones normally increase chemical processes occurring within the cells of the body, especially those related to metabolism; however, in hyperthyroidism, the excessive hormone levels push the cells and body into overdrive, resulting in increased metabolism with concurrent weight loss, anxiety, and diarrhea, among other symptoms. There is no known genetic predisposition for hyperthyroidism, but it is quite common in cats. In fact, hyperthyroidism is the most common hormonal (endocrine) disease in the cat population, often seen in late middle-aged and older cats. (The mean age of discovery is approximately 13 years, with a range of 4-22 years.) Symptoms and Types Involves many organ systems due to the overall increase in metabolism Weight loss Increased appetite Unkempt appearance Poor body condition Vomiting Diarrhea Increased thirst (polydipsia) Increased urine (polyuria) Rapid breathing (tachypnea) Difficulty breathing (dyspnea) Heart murmur; rapid heart rate; particularly an abnormal heart beat known as a “gallop rhythm” Hyperactivity Aggression Enlarged thyroid gland, which can be felt as a lump on the neck Thickened nails Less than 10 percent of cats suffering from hyperthyroidism are referred to as apathetic. These patients exhibit atypical signs such as poor appetite, loss of appetite, depression, and weakness. Causes Overfunctioning thyroid nodules (where the thyroid nodules produce excess thyroid hormones outside of the control of the pituitary gland) Rarely, thyroid cancer Some reports have linked hyperthyroidism in cats to some canned food diets Advancing age increases risk Diagnosis The signs of feline hyperthyroidism can overlap with those of chronic renal failure, chronic hepatic disease, and cancer (especially intestinal lymphoma). These diseases can be excluded on the basis of routine laboratory findings and thyroid function tests. Your veterinarian will conduct a battery of tests to zero in on a reliable diagnosis. Thoracic radiography and echocardiography may be useful in assessing the severity of myocardial disease. Abdominal ultrasound may be useful for exploring underlying renal disease. Thyroid gland scintigraphy (a diagnostic test in which a two-dimensional picture of a body radiation source is obtained through the use of radioisotopes) can be used to diagnose hyperthyroidism and to determine the location of abnormal thyroid tissue. A high concentration of T4 (tetraiodothyronine) in the blood serum is the most common finding, confirming the diagnosis of hyperthyroidism. In some cases, however, the T4 levels may be in the normal range, making a diagnosis of hyperthyroidism more difficult. This is especially true in the early stages of this disease. If your cat is showing the symptoms of hyperthyroidism but the blood tests are not conclusive, you will need to return to your veterinarian for further blood tests. 1 2 Next polyuriaExcessive urination polydipsiaA medical condition involving excessive thirst radiographyA procedure of imaging internal body structures by exposing film tachypneaThe term for a quick heartbeat thyroid glandA gland found in the neck of humans and animals that secretes glands responsible for metabolic rate, calcitonin, and others. pituitary glandThe gland that is found at the bottom of the brain whose job is to maintain appropriate levels of hormones in the blood renal failureThe failure of the kidneys to perform their proper functions metabolismThe group of processes that involve the use of nutrients by the body echocardiographyA procedure that is used to evaluate the health and structures of the heart dyspneaHaving a hard time breathing; breathing takes great pains hepaticReferring to the liver inhibitTo slow something down or cause it to stop lymphomaA term for a type of neoplasm that is made up of lymphoid tissue; these masses are usually malignant in nature atypicalDeviating from the normal; not typical.